EFFECT OF IN-VITRO GENERATION OF OXYGEN-FREE RADICALS ON T-CELL FUNCTION IN YOUNG AND OLD RATS

T cells from young (6 months) and old (24 months) male Fischer 344 rat s were isolated and exposed to three different oxidative stress condit ions: (a) reactive oxygen species generated by xanthine-xanthine oxida se (X/XO), (b) hydrogen peroxide (H2O2), and (c) hyperthermia (43 degr ees C for 1 h). After oxidative stress treatment, the induction of pro liferation and IL-2 production by concanavalin A (Con A) was measured. Exposure of T cells to X/XO or H2O2 resulted in suppression of prolif eration and IL-2 expression, and the suppressive effect was more prono unced in T cells from young rats than in T cells from old rats. Simila rly, hyperthermia caused inhibition of proliferation and IL-2 expressi on in T cells from young and old rats. Addition of antioxidant to cult ured cells only slightly attenuated the effects of X/XO and H2O2 on T cell function; however, antioxidant had no effect on heat shock-mediat ed inhibition of proliferation in young or old rats. Because IL-2 play s a crucial role in T cell proliferation and because the transcription factor NFAT (nuclear factor of activated T cell) plays a major role i n the regulation of IL-2 transcription, the induction of NFAT as well as NF-kappa B and AP-1 DNA binding activities in nuclear extracts of t he X/XO-treated and untreated control cells was measured using a gel s hift assay. The ability of nuclear extracts to bind NFAT or NF-kappa B oligonucleotide decreased in the X/XO-treated cells from young and ol d rats compared to the untreated controls. Therefore, these data imply that reactive oxygen species generated by the X/XO system alter the d istal step of mitogen-mediated signal transduction, i.e., transcriptio n factors that regulate IL-2 transcription. (C) 1998 Elsevier Science Inc.